Personalization of auditory stimulus

ABSTRACT

Technology presented herein increases a user&#39;s enjoyment of sound by personalizing an audio signal so that the user perceives the audio signal as if the user had ideal hearing and/or desired hearing. In one embodiment, headphones on a user&#39;s head include a sensor and a speaker. While the speaker plays an audio signal to the user, the sensor records the user&#39;s response to the audio signal. The sensor can be a microphone, a brainwave sensor, an EEG sensor, etc. The user&#39;s response can be the audio response inside the user&#39;s ear, the brainwave response associated with the user, electrical skin response associated with the user, etc. Based on the measured response, and based on the knowledge of how other people perceive sound, the audio signal is modified to compensate for the difference between the user&#39;s hearing and the ideal hearing and/or desired hearing, therefore increasing the user&#39;s enjoyment of sound.

This application is a continuation of the U.S. patent application Ser.No. 15/247,688 filed on Aug. 25, 2016, which is a continuation of U.S.patent application Ser. No. 15/154,694 filed on May 13, 2016, now U.S.Pat. No. 9,497,530, which claims priority to the following Australianprovisional patent applications: Australian Provisional PatentApplication Serial Number 2015903530 filed Aug. 31, 2015; the AustralianProvisional Patent Application Serial Number 2016900105 filed Jan. 14,2016; and the Australian Provisional Patent Application Serial Number2016900106 filed Jan. 14, 2016; all of which are incorporated herein byreference in their entirety.

TECHNICAL FIELD

The present invention relates generally to the provision of an auditorystimulus by one or more loudspeakers, such as consumer headphones orearphones, and in particular to the personalization of the auditorystimulus produced by such loudspeakers in order to adjust for the uniquecharacteristics of a user's hearing.

BACKGROUND

Audio headphones are generally designed to transduce an electronic inputsignal to an acoustic wave across a frequency range with the expectationthat all users hear in the same way. Standard audio headphones areunable to take into account differences in conductive and sensorineuralhearing in users. Hearing loss is experienced by many people, especiallywith aging, and even people with “normal hearing” have varyingsensitivity to different frequencies of sound. The clinical definitionof “normal” hearing is wide (i.e., thresholds between −10 to +25 dBacross frequency).

In order to select headphones that are best suited to an individualuser, that user is currently limited to trying a range of headphones andpicking those that best “fit” that user's hearing. Users will tryvarious on-ear, over-ear or in-ear headphones or earbuds and make asubjective assessment of the best sound reproduction available for them.

While some headphones allow a user to manually adjust audioequalization, either by operation of controls available on theheadphones themselves or via a wired or wireless connection to asmartphone app or the like, such equalization is once again based onmanual adjustment by the user rather than audiometric information.

It would be desirable to provide a method of personalizing an auditorystimulus, produced by one or more loudspeakers configured to be held inplace close to or in a user's ear, that uses subjective and/or objectiveaudiometric information to automatically adapt said auditory stimulus tobe well suited to a user's hearing profile. It would also be desirableto provide a method of personalizing an auditory stimulus produced byone or more loudspeakers that ameliorates or overcomes one or moredisadvantages of known sound reproduction techniques.

SUMMARY

Presented here is an apparatus and method to increase a user's enjoymentof sound by personalizing an audio signal so that the user perceives theaudio signal as if the user had ideal hearing and/or desired hearing. Inone embodiment, headphones on a user's head include a sensor and aspeaker. While the speaker plays an audio signal to the user, the sensorrecords the user's response to the audio signal. The sensor can be amicrophone, a brainwave sensor, an EEG sensor, etc. The user's responsecan be the audio response inside the user's ear, the brainwave responseassociated with the user, the electrical skin response associated withthe user, etc. Based on the measured response, and based on theknowledge of how people perceive sound, the audio signal is modified tocompensate for the difference between the user's hearing and idealhearing and/or desired hearing, therefore increasing the user'senjoyment of sound.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and characteristics of the presentembodiments will become more apparent to those skilled in the art from astudy of the following detailed description in conjunction with theappended claims and drawings, all of which form a part of thisspecification. While the accompanying drawings include illustrations ofvarious embodiments, the drawings are not intended to limit the claimedsubject matter.

FIG. 1 depicts a set of headphones including a dry electrode orcapacitive sensors, speakers, and a signal processing module, accordingto one embodiment.

FIG. 2 is a schematic diagram depicting the electrical components of thesignal processing module located within each of the housings of theheadphones, according to one embodiment.

FIG. 3 depicts an alternative arrangement to that shown in FIG. 1,according to one embodiment.

FIG. 4A is a schematic diagram of the electrical components of thedigital signal processing module of the earbud arrangement shown in FIG.3, according to one embodiment.

FIG. 4B shows a schematic of a probe for measurement ofdistortion-product otoacoustic emissions (DP-OAE), according to oneembodiment.

FIG. 4C shows a frequency response of each speaker in FIG. 4B, accordingto one embodiment.

FIG. 4D is a flowchart of the digital signal processing algorithm formeasuring the hearing transfer function and/or the hearing profileassociated with the user, using the probe in FIG. 4B, according to oneembodiment.

FIG. 5 is a flowchart depicting the signal processing operationperformed by the signal processing modules depicted in FIGS. 2 and 4,according to one embodiment.

FIG. 6 depicts the frequency response in the time domain of arepresentative normal ear compared to an ear with mild hearing loss.

FIG. 7 shows the RMS amplitude of an auditory evoked potential responsein the frequency domain of a normal ear and an ear with mild hearingloss.

FIG. 8A shows Fourier analysis of the low-pass filtered outputted soundsignal and EEG (frequency following response), according to oneembodiment.

FIG. 8B is a flowchart of a technique to determine a low frequencyportion of the hearing transfer function, according to one embodiment.

FIG. 9A shows information about the high frequency hearing which isobtained by analyzing the EEG signal after acoustic transients,according to one embodiment.

FIG. 9B is a flowchart of a technique to determine a high frequencyportion of the hearing transfer function, according to one embodiment.

FIG. 10 depicts an example of distortion product OAE fine structure,according to one embodiment.

FIG. 11 depicts an embodiment of this invention where the OAE probe alsofunctions as a set of headphones for consumer audio use.

DETAILED DESCRIPTION

Terminology

Brief definitions of terms, abbreviations, and phrases used throughoutthis application are given below.

“Ideal hearing” is the average level of perception across the audiblefrequency spectrum of young, ontologically normal ears when a constantamplitude across the audible frequency spectrum is provided as the audiostimulus.

“Desired Hearing” is the desired level of perception across the audiblefrequency spectrum when a constant amplitude across the audiblefrequency spectrum is provided as the audio stimulus. The desiredhearing profile can be arbitrarily set and may or may not be set asideal hearing profile.

“Normal hearing” is a range around the ideal hearing. Many people areconsidered to have “normal hearing,” meaning that their hearingsensitivity is within 15-20 dB of ideal hearing across frequencies.

“Hearing transfer function” correlates a given input frequency and acorresponding input amplitude associated with an input audio signal, toa perceived amplitude of the given input frequency.

“Hearing profile” comprises a set of measurements of a person's hearingbased on which that person's hearing transfer function can be estimated.

“Channels of audio” are separate audio signals coming from one source orseparate sources. Multiple channels of audio could be combined andplayed through the same speaker or they could be played from separatespeakers.

“Statistical information representing data regarding human hearingprofiles,” i.e., “statistical information,” is a collection ofstatistics regarding the hearing profiles of many people. Statisticalinformation comprises one or more of: the average of human hearingprofiles at one or more frequencies, the standard deviation of humanhearing profiles at one or more frequencies, hearing profiles or hearingtransfer functions of individual listeners, and correlations betweentypes of objective or subjective hearing data.

Reference in this specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the disclosure. The appearances of the phrase “in one embodiment” invarious places in the specification do not necessarily all refer to thesame embodiment, nor are separate or alternative embodiments mutuallyexclusive of other embodiments. Moreover, various features are describedthat may be exhibited by some embodiments and not by others. Similarly,various requirements are described that may be requirements for someembodiments but not others.

Unless the context clearly requires otherwise, throughout thedescription and the claims, the words “comprise,” “comprising,” and thelike are to be construed in an inclusive sense as opposed to anexclusive or exhaustive sense; that is to say, in the sense of“including, but not limited to.” As used herein, the terms “connected,”“coupled,” or any variant thereof, means any connection or coupling,either direct or indirect, between two or more elements. The coupling orconnection between the elements can be physical, logical, or acombination thereof. For example, two devices may be coupled directly,or via one or more intermediary channels or devices. As another example,devices may be coupled in such a way that information can be passedtherebetween, while not sharing any physical connection with oneanother. Additionally, the words “herein,” “above,” “below,” and wordsof similar import, when used in this application, shall refer to thisapplication as a whole and not to any particular portions of thisapplication. Where the context permits, words in the DetailedDescription using the singular or plural number may also include theplural or singular number respectively. The word “or,” in reference to alist of two or more items, covers all of the following interpretationsof the word: any of the items in the list, all of the items in the list,and any combination of the items in the list.

If the specification states a component or feature “may,” “can,”“could,” or “might” be included or have a characteristic, thatparticular component or feature is not required to be included or havethe characteristic.

The term “module” refers broadly to locally executed software, softwareexecuted in the cloud, hardware, or firmware components (or anycombination thereof). Modules are typically functional components thatcan generate useful data or other output using specified input(s). Amodule may or may not be self-contained. An application program (alsocalled an “application”) may include one or more modules, or a modulemay include one or more applications.

The terminology used in the Detailed Description is intended to beinterpreted in its broadest reasonable manner, even though it is beingused in conjunction with certain examples. The terms used in thisspecification generally have their ordinary meanings in the art, withinthe context of the disclosure, and in the specific context where eachterm is used. For convenience, certain terms or elements may behighlighted, for example, by use of capitalization, italics, and/orquotation marks. The use of highlighting has no influence on the scopeand meaning of a term; the scope and meaning of a term are the same, inthe same context, whether or not the term is highlighted. It will beappreciated that the same element can be described in more than one way.

Consequently, alternative language and synonyms may be used for any oneor more of the terms discussed herein, but special significance is notto be placed upon whether or not a term is elaborated or discussedherein. A recital of one or more synonyms does not exclude the use ofother synonyms. The use of examples anywhere in this specification,including examples of any terms discussed herein, is illustrative onlyand is not intended to further limit the scope and meaning of thedisclosure or of any exemplified term. Likewise, the disclosure is notlimited to various embodiments given in this specification.

Headphones

FIG. 1 depicts a set of headphones including a dry electrode orcapacitive sensors, speakers and an electronics module including asignal processing module, according to one embodiment. A set ofheadphones 10 includes the speakers 12 and 14 located within cups 16 and18 in order to position the speakers 12 and 14 close to both of a user'sears. The two cups 16 and 18 are coupled to an adjustable head supportmember 20. To the rear of the cups 16 and 18 are located housings 22 and24 housing electrical/electronic modules and interface units, thefunction of which is described below. In addition, the headphones 10include dry electrode or capacitive sensors 26, 28 and 30 positioned tomake contact with the user's head so as to measure auditory evokedpotentials generated by the user in response to an auditory stimulusapplied to one or both of the user's ears through the speakers 12 and14. The headphones 10 can further include external microphones 32 and34.

FIG. 2 is a schematic diagram depicting the electrical componentslocated within each of the housings 22 and 24 of the headphones 10,according to one embodiment. The electronics module 40 includes a signalprocessing module 42, wired or wireless connections 60 and 62 (such asan audio input jack or Bluetooth module), and an external microphone 32,34 for noise cancellation. The signal processing module 42 furtherincludes analog-to-digital and/or digital-to-analog converters 48 to 54for interfacing with external digital or analog devices, together with apower source 56 providing power to the signal processing module 42.Interconnected to the signal processing module 42 are an interface forexternal microphones 32 and 34, a wired or wireless connection 60 forreceiving digital or audio analog signal inputs, as well as a wired orwireless connection 62 for digital data transfer, for example, to changestored settings maintained in the memory 46 of the signal processingmodule 42 to control operation of the processor 44 or to outputaudiometric data for display on a smartphone. The wired connection canbe a phone jack, while the wireless connection can be a Bluetoothmodule. In this exemplary embodiment, the external microphones 32 and 34are used by the signal processing module 42 to record ambient noise foruse in noise cancellation operations. However, in other embodiments thesignal processing module 42 may exclude results if ambient noiserecorded by the microphones is too high.

The dry electrode or capacitive sensors 26, 28, and 30 areinterconnected via the analog-to-digital converter 54. The loudspeakers12 and 14 are interconnected to the signal processing module 42 by meansof a digital-to-analog converter 52 and amplifier. Optionally, aninternal microphone 64 is provided for calibration of the operations ofthe headphones 10.

The signal processing module 42 is also adapted to receive audiometricdata 66 via the wired or wireless connection 62. The audiometric data 66characterizes the audible threshold or equal loudness curve of the useracross a frequency range. In one or more embodiments, that audiometricdata 66 may be provided by an external source; for example, the resultsof an audiogram testing process may be provided by an audiologist. Theaudiometric data 66 can be input via a wired or a wireless connection 62into the signal processing module 42.

Optionally, user controls, such as a button 68, may be provided on theheadset 10 to enable the user to generate input signals to the processor44 in response to the user's perception of auditory stimuli provided bythe loudspeakers 12 and 14.

FIG. 3 depicts an alternative arrangement to that shown in FIG. 1,according to one embodiment. An earbud 70 arrangement adapted to belocated within the ear canal of one of a user's ears includes twospeakers 84 and 86, an internal microphone 82, and an optional externalmicrophone. The earbud 70 is connected to an electronics module 72similar to that located in the housings 22 and 24 of the headset 10depicted in FIG. 1.

FIG. 4A is a schematic diagram of the electrical and electroniccomponents of the earbud 70 arrangement shown in FIG. 3, according toone embodiment. The electronics module 72 includes a signal processingmodule 74, wired or wireless connections 76 and 78 (such as an audioinput jack or wireless module), and an optional external microphone 80for noise cancellation. The internal microphone 82 for calibration andfor measurement of otoacoustic emissions (OAEs) is co-located with theearbud 70, as are the loudspeakers 84 and 86 that form part of theearbud 70. In this arrangement, two speakers per ear are included toallow measurement of distortion-product otoacoustic emissions.Distortion-product otoacoustic emissions (DP-OAEs) are generated in thecochlea in response to two tones of a given frequency and sound pressurelevel presented in the ear canal. DP-OAEs are an objective indicator ofnormally functioning cochlea outer hair cells. Other types ofotoacoustic emissions may only require one speaker per ear canal.

The processing unit 74 includes a processor 88 for executing operationsof the processing unit, a memory 90 for storing programming instructionsand data used by the processor 88 during program execution, a powersource 92, such as a battery, for providing power to the variouselectronic components in the processing unit 74, as well asanalog-to-digital or digital-to-analog converters 94, 96, and 98 inorder to enable the processing unit 74 to interface with the variousdevices such as external microphone 80, internal microphone 82, andspeakers 84 and 86. In addition, the processing unit 74 is adapted toreceive audiometric data 100 via wired or wireless connection 78 from anexternal source, such as an audiogram test result provided by anaudiologist.

FIG. 4B shows a schematic of a probe for measurement ofdistortion-product otoacoustic emissions, according to one embodiment.DP-OAE probe 1 includes two balanced armature speakers, a woofer 2 and atweeter 3, and a microphone 9. The microphone 9 is connected to apreamplifier 4 and analog-to-digital converter 5. The speakers 2 and 3are connected to a dual-channel headphone amplifier 6, which isconnected to a dual-channel digital-to-analog converter 7. Converters 5and 7 are connected to a digital signal processor 8, which providesequalization to control the stimuli loudness in test mode, playbackequalization (if desired) and a digital crossover to the two receivers.An embodiment of this invention includes one probe for each ear.

FIG. 4C shows a frequency response of each speaker in FIG. 4B, accordingto one embodiment. Both woofer 2 and tweeter 3 are capable of generatingstimuli of sufficient loudness over the standard audiological testingfrequency and loudness range, which is approximately 250 Hz to 8000 Hzup to 80 dB sound pressure level (SPL). Using both speakers 2 and 3 witha crossover in playback mode would provide superior coverage of thefrequency range. The data has been adapted from the datasheets of thecommercially available Knowles HODVTEC-31618-000 and SWFK-31736-000receivers.

FIG. 4D is a flowchart of the digital signal processing algorithm formeasuring the hearing transfer function and/or the hearing profileassociated with the user, using the probe in FIG. 4B, according to oneembodiment. In step 11, the digital signal processor 8 (shown in FIG.4B) receives an audio input which may be the test audio signal and/orthe audio playback signal comprising audio content such as music,speech, environment sounds, animal sounds, etc. The audio signals can beinput via an analog or digital, wired or wireless audio interface 76(shown in FIG. 4A), or can be stored in memory 90 (in FIG. 4A), and/ormemory 46 (in FIG. 2). In step 13, the processor 8 determines whetherthe mode is in a testing or playback mode. In step 15, if the mode istesting mode, the processor 8 applies a first and a second filter to theaudio input, corresponding to the woofer 2 (in FIG. 4B) and the tweeter3 (in FIG. 4B), respectively. In one embodiment, the first and thesecond filter are no-operation filters or filters that provide a flatfrequency response from the speakers allowing calibrated test stimuli tobe played to the speakers 2 and 3.

In step 17, if the mode is playback mode, the processor 8 applies athird and a fourth filter to the audio input, corresponding to thewoofer 2 and the tweeter 3, respectively. In one embodiment, the thirdand the fourth filters include low-pass and high-pass filtersrespectively, creating a digital crossover. In step 19, the processor 8sends the audio signal to the digital-to-analog converter 7 (in FIG.4B). Those skilled in the art will recognize there are many variationson the methodology of applying switchable crossovers, which could bedone either digitally or electronically.

FIG. 5 is a flowchart depicting the signal processing operationperformed by the signal processing modules depicted in FIGS. 2 and 4,according to one embodiment. Each memory 46 and/or 90, in step 110,stores a copy of the hearing transfer function for each of the user'sears. Each memory 46 and/or 90, in step 112, further stores an estimateof the accuracy and completeness of the hearing transfer function, andin step 114, each memory 46 and/or 90 stores a user preference for adegree of correction to be applied to the hearing transfer function. Inanother embodiment, the memory 46 and/or 90 can be a remote databasestoring various needed information.

In step 116, each processor 8, 44 or 88 receives an audio signalcorresponding to a sound that is desired to be reproduced by theloudspeakers of either the headset 10 or the earbud 1, 70. Optionally,an input audio signal is received at step 118 by the external microphone32, 34, and/or 80, and at step 120, the processor 8, 44, and/or 88performs a noise cancellation function in order to minimize the impactof ambient noise on the audio signal input in step 116.

At step 122, the processor 8, 44, and/or 88 uses the stored hearingtransfer function, the stored estimate of the accuracy and completenessof the hearing transfer function, and optionally the user preference fora degree of correction to be applied to the hearing transfer function,to make frequency-specific adjustments for amplitude and phase toautomatically compensate for a user's hearing transfer function.

In some circumstances, the correction need not attempt to completelycorrect the sound. For example, only a partial correction may be appliedif the accuracy or completeness of the hearing transfer function is low,as is described below, or according to a preference of the user. Theprocessor 8, 44, or 88 may also be configured to limit a sound outputsignal that may be perceived to be dangerously loud by a user.

At step 122, the processor 8, 44, and/or 88 modifies the input audiosignal so that the user perceives the input audio signal, as if the userhad ideal hearing and/or desired hearing. The processor 8, 44, and/or 88can modify the amplitude, the phase, the latency, etc., of the inputaudio signal. Since the response of a human ear to varying amplitudes ata given frequency is not linear, the processor 8, 44, and/or 88 candetermine how to modify the input audio signal in several ways.

In various embodiments described herein, the desired hearing can be setby the user. For example, the user can specify to amplify a specifiedfrequency range, such as low frequencies, mid frequencies, or highfrequencies. In another example, the user can specify to attenuate aspecified frequency range, such as low frequencies, mid frequencies, orhigh frequencies. The amplification and the attenuation can happenindependently, or at the same time.

According to one embodiment, at step 126, the processor 8, 44, and/or 88receives a plurality of hearing profiles associated with a plurality ofpeople. The plurality of hearing profiles can be received via a wired orwireless connection 62 (in FIG. 2), and/or 78 (in FIG. 4A), or can bestored in memory 46 (in FIG. 2), and/or 90 (in FIG. 4A). A hearingprofile in the plurality of hearing profiles comprises a hearingtransfer function associated with a person, and a perceived amplitude ofthe input frequency as the input amplitude associated with the inputfrequency varies.

The processor 8, 44, and/or 88 finds one or more similar hearingprofiles that closely match the hearing transfer function associatedwith the user. Based on the similar hearing profiles, the processor 8,44, and/or 88 determines by how much to vary the input audio signal sothat the user perceives the input audio signal, as if the user had idealhearing and/or desired hearing.

For example, the hearing transfer function associated with a userspecifies that an input audio signal comprising 1000 Hz at 70 dB, isperceived by the user as having 25 dB, while an input audio signalcomprising 2000 Hz at 70 dB, is perceived by the user is having 50 dB.The processor 8, 44, and/or 88 determines a set of similar hearingprofiles from the plurality of hearing profiles, where a similar hearingprofile is associated with a person who perceives 1000 Hz to be roughly25 dB (i.e., 20 dB to 30 dB) softer than 2000 Hz. The hearing profilescontain information regarding what modified amplitude the 1000 Hz signalneeds to be so that the person perceives the amplitude of an inputsignal of 1000 Hz at 70 dB to be the same as the amplitude of an inputsignal of 2000 Hz at 70 dB. According to one embodiment, the processor8, 44 and/or 88 averages the modified amplitudes associated with thesimilar hearing profiles, to obtain the modified amplitude associatedwith the user. The processor 8, 44, and/or 88, at step 122, thenmodifies the input signal accordingly.

According to another embodiment, the hearing transfer functionassociated with a user specifies that an audio signal comprising 1000 Hzat 70 dB, is perceived by the user as having 45 dB. The processor 8, 44,and/or 88 determines a set of hearing profiles, in which a personperceives 1000 Hz to be roughly 25 dB softer than the input amplitude.The hearing profiles contain information regarding what modifiedamplitude the 1000 Hz signal needs to be so that the person perceives aninput audio signal of 1000 Hz at 70 dB to be 70 dB. According to oneembodiment, the processor 8, 44 and/or 88 averages the modifiedamplitudes associated with the hearing profiles, to obtain the modifiedamplitude associated with the user. The processor 8, 44, and/or 88 thenmodifies the input signal accordingly.

In another embodiment, the processor 8, 44, and/or 88 does not receivethe plurality of hearing profiles associated with the plurality ofpeople. Instead, the processor measures a hearing profile associatedwith the user, by playing an input audio signal comprising varyingamplitudes at a single frequency. The input audio signal can be agenerated test audio signal, and/or a content audio signal comprisingmusic, speech, environment sounds, animal sounds, etc. For example, theinput audio signal can include the content audio signal with an embeddedtest audio signal.

In this case, for example, the hearing transfer function associated witha user specifies that an audio signal comprising 1000 Hz at 70 dB, isperceived by the user as having 60 dB while a 1500 Hz at 70 dB, isperceived by the user is having 50 dB. The hearing profile associatedwith the user specifies that, in order for the user to perceive 1000 Hzand 1500 Hz at equal loudnesses there must be a relative increase in the1500 Hz loudness of 10 dB. Thus, the processor 8, 44, and/or 88, in step122, then modifies the input signal accordingly.

According to one embodiment, at step 126, the processor 8, 44, and/or 88receives statistical information representing data regarding humanhearing profiles. The statistical information can be received via awired or wireless connection 62 (in FIG. 2), and/or 78 (in FIG. 4A), orcan be stored in memory 46 (in FIG. 2), and/or 90 (in FIG. 4A). Forexample, statistical information representing data regarding humanhearing profiles could include the average and standard deviation ofhuman hearing profiles at one or more frequencies. It may also includecorrelations between types of objective or subjective hearing data.

Based on the statistical information, the processor 8, 44, and/or 88determines one or more similar hearing profiles that closely match thehearing transfer function associated with the user. For example, basedon statistical information the processor constructs a plurality ofhearing profiles that are similar to the hearing transfer functionassociated with the user. Based on the similar hearing profiles, theprocessor 8, 44, and/or 88 determines by how much to vary the inputaudio signal so that the user perceives the input audio signal, as ifthe user had ideal hearing and/or desired hearing.

In various embodiments, the processor 8, 44, and/or 88, continues torefine the hearing transfer function associated with a user, as the usercontinues to listen to audio.

The modified audio signal from the processor 8, 44, or 88 is then outputat step 124 to the loudspeakers 12 and 14 or 84 and 86 to produce anauditory stimulus to one or both of the user's ears.

The hearing transfer function stored in the memory 46 or 90 may begenerated in a number of ways, namely by subjective measurement, byotoacoustic emissions (OAE), auditory evoked potentials (AEP), or otherobjective tests such as the middle ear reflex.

Subjective Measurements

Audiometric measurements performed by an audiologist or via a computerprogram or the like can be provided to the signal processing modules 42and 74 from an external source.

Alternatively, the button 68 or other user controls on the headphones 10can be used by a user to directly acquire auditory threshold data byhaving the user press the button in response to sound signals. Forexample, an auditory stimulus can be played to the user at increasing ordecreasing amplitudes at different frequencies across the audiblefrequency range. The user presses a button on headphones 10 to provide auser-generated input signal when the auditory stimulus is at orproximate to the user's audible threshold for each different frequency.

A convenient psychophysical test is a pure tone audiometry with whichthe user interacts in order to determine their audible threshold ofhearing. Alternatively, a test can be conducted at the same loudness butat different frequencies, namely an “Equal Loudness Contours” test.

Otoacoustic Emissions (OAE)

Otoacoustic emissions can be measured within the user's ear canal andthen used to determine thresholds at multiple frequencies or relativeamplitudes of the otoacoustic emissions at multiple frequencies to oneor more suprathreshold sound levels in order to develop the frequencydependent hearing transfer function of the user's ear(s). Stimulusfrequency OAE, swept-tone OAE, transient evoked OAE, DP-OAE, or pulsedDP-OAE can be used for this purpose.

The amplitude, latency, hearing threshold, and/or phase of the measuredOAEs can be compared to response ranges from normal-hearing andhearing-impaired listeners to develop the frequency dependent hearingtransfer function for each ear of the user.

Since DP-OAEs are best measured in a sealed ear canal with two separatespeakers/receivers packed into each ear canal, the use of OAEs is bestsuited for the earbud implementation depicted in FIGS. 3 and 4.

In the case of OAEs, one stimulus frequency/loudness combination yieldsa response amplitude. The measurement of multiple frequencies in thismanner yields a plot of response amplitude versus frequency, which isstored in the memory 46 or 90 of the signal processing modules 42 or 74,or can be stored in a remote database. Many OAE techniques rely upon themeasurement of one frequency per stimulus; however, the swept tone OAEmeasures all frequencies in the range of the sweep. Nevertheless, thehearing transfer function remains the same regardless of the measuringmethod used, that is, the hearing transfer function comprises a plot ofthe signal amplitude versus frequency of the OAE evoked in the user'sear upon application of an input audio signal. The hearing transferfunction can also comprise the input amplitude associated with the inputfrequency.

In this exemplary embodiment, in order to determine the hearing transferfunction for a user's ear, the processor 8, 44, and/or 88 captures datapoints for an input audio signal comprising a number of frequencies, forexample, 500, 1000, 2000 and 4000 Hz, which are typically the samefrequencies used in the equalizer that acts upon the output sound signalto the loudspeakers 12 and 14, 84 and 86, 2 and 3. At any one frequency,the processor measures the response to an input audio signal at reducinglevels, for example, at 70 dB, 60 dB, 50 dB, 40 dB, etc., until there isno longer a measurable response. The processor 8, 44, and/or 88 recordsthe data point at that time. It will be appreciated that in otherembodiments, different methods, such as curve fitting or measuring aprofile at a single loudness level, can be used to determine the hearingtransfer function. The input audio signal can include a test audiosignal, and/or a content audio signal comprising music, speech,environment sounds, animal sounds, etc. For example, the input audiosignal can include the content audio signal with an embedded test audiosignal.

In-situ calibration of the speakers to the user's ear canal can beperformed by the processor 8, 44, and/or 88 prior to making an OAEmeasurement. In this context “in-situ” refers to measurements made attimes when the speakers and microphone are situated for use inside theear canal. Where the acoustic characteristic of the speakers are known,the acoustic impedance of the ear can be calculated from this data andutilized for deriving corrections.

In one or more embodiments, in-situ calibration can be done by playing atest audio signal, such as a chirp, or the content signal, covering thefrequency range of the speakers, recording the frequency response withthe microphone, and adjusting output by changing the equalizer settingsto make a flat frequency response of the desired loudness.

In other embodiments, this calibration can be done in real time to anyplayback sound (e.g., music, or any audio comprising content) byconstantly comparing the predicted output of the speakers in thefrequency domain given the electric input to the speaker to themicrophone and altering the equalizer gains until they match. Thein-situ calibration accounts for variations in different users' externalportion of the ear and variations in the placement of earbuds. If noaudiometric data is yet available, then the in-situ calibration alonecan be used for adjusting the sound.

Any variation with an internal microphone can use that microphone forin-situ calibration of the speakers performed every time the user placesthe headphones on.

Auditory Evoked Potentials (AEP)

AEPs involve the measurement of nanovolt range signals from the dryelectrode or capacitive sensors 26, 28, and 30 depicted in FIG. 1.

In order to boost the signal-to-noise ratio of the AEPs, multiplerepetitions of auditory stimuli are generally required to be applied.

Traditionally, AEPs are measured using wet electrodes after preparingthe skin by gentle abrasion. This is impractical for use in consumeraudio headphones, which is why dry electrodes and/or capacitive sensorsare used in this case. In light of the reduced signal-to-noise ratio,multiple repetitions of stimuli are generally required, which means thatthe hearing transfer function estimation generally takes a longer periodof time or, alternatively, is less accurate than in the case when wetelectrodes are used.

Any AEP can be measured, such as auditory brainstem response, midlatency response, cortical response, acoustic change complex, auditorysteady state response, complex auditory brainstem response,electrocochleography, cochlear microphonic, or cochlear neurophonicAEPs.

The frequency dependent hearing transfer function for each ear isdetermined by the processor 8, 44, and/or 88 by using frequency-specificstimuli, such as tones or band-limited chirps, or audio content signal,such as music or speech, which are used as the auditory stimuli appliedto the user's ear, and thereafter determining either frequency-specificthresholds or using one or more suprathreshold sound levels anddetermining relative amplitudes and/or latencies of the AEP responses.

Comparisons of amplitude, latency, hearing threshold and/or phase can bemade to response ranges from normal-hearing and hearing-impairedlisteners to develop an hearing transfer function for each ear. Theresponse ranges of normal-hearing and hearing-impaired listeners can bemaintained in the memory 46 or 90 for use by the processor 8, 44, and/or88 in such an operation.

The exact processing operation performed by the processor 8, 44, and/or88 to detect an AEP response is different for each of the AEP methodsdescribed above because the time course of the characteristic wave formfor each AEP is different.

In general, methods applied by the processor 8, 44, and/or 88 includethe use of a peak picking algorithm, or a window root mean square (RMS)measure of the response compared to baseline RMS or a frequency-specificRMS of the signal above baseline noise. However, other methods are welldescribed, such as in Valderrama, Joaquin T., et al. “Automatic qualityassessment and peak identification of auditory brainstem responses withfitted parametric peaks.” Computer methods and programs in biomedicine114.3 (2014): 262-275.

FIG. 6 depicts the frequency response in the time domain of arepresentative normal ear compared to an ear with mild hearing loss.

FIG. 7 shows the RMS amplitude of an auditory evoked potential responsein the frequency domain of a normal ear and an ear with mild hearingloss. The solid line depicts an hearing transfer function associatedwith the normal ear, and the dashed line depicts an hearing transferfunction associated with the ear with a mild hearing loss.

Two AEPs have been found to be particularly convenient in relation toone or more embodiments of the invention, namely auditory steady stateresponse (ASSR) and complex auditory brainstem response (cABR). ASSR isparticularly convenient for this application since the detection of aresponse is carried out statistically by published methods, including:

-   -   Mühler, Roland, Katrin Mentzel, and Jesko Verhey. “Fast        hearing-threshold estimation using multiple auditory        steady-state responses with narrow-band chirps and adaptive        stimulus patterns.” The Scientific World Journal 2012 (2012).

Other features/benefits of the above-described embodiment include:

-   -   Multiple frequencies can be tested simultaneously and both ears        can be tested at the same time. Phase information is also        available.    -   Use of cABR involves recording electroencephalogram (EEG)        activity while a complex sound is being played to the user.    -   Multiple responses to the same stimuli are usually averaged by        the processor in time or frequency domains.    -   Low frequency (typically less than 1 kHz) sounds are followed        with a delay by the EEG wave form (frequency following        response).    -   Transient features of sound, such as sudden onsets at the start        of speech, a musical note, or a drum beat, cause extra cABR-like        waveforms in the EEG waveform.    -   cABR analyses can also be adapted to estimate an ear's hearing        transfer function in response to continuous sound, such as        music.

FIG. 8A shows Fourier analyses of the low-pass filtered outputted soundsignal and EEG (frequency following response), according to oneembodiment. The low-pass filtered output signal and the EEG frequencyfollowing response provide the low frequency part of the hearingtransfer function. Frequency domain averaging is required due to the lowsignal-to-noise ratio (SNR).

FIG. 8B is a flowchart of a technique to determine a low frequencyportion of the hearing transfer function, according to one embodiment.In step 800, the processor 8, 44, and/or 88 repeatedly performs Fouriertransforms and/or fast Fourier transforms of the audio signal and theresponse, such as an EEG response. The audio signal comprises multiplefrequency ranges, such as 125, 250, 500, and 1000 Hz. In step 810, theprocessor 8, 44, and/or 88 determines loudness for each frequency rangeand the amplitude of the detected response, such as an EEG response. Instep 820 the processor 8, 44, and/or 88 continuously builds an averagevalue of the multiple frequency range/loudness pairs. This technique iseasier and more accurate than the high frequency version; but the bodylow-pass filters the response, so this technique works less well withincreasing frequency.

FIG. 9A shows information about the high frequency hearing which isobtained by analyzing the response, such as an EEG response signal afteracoustic transients, according to one embodiment. Element 900 is theinput audio signal. Element 910 is the signal obtained from a sensor,such as an EEG sensor. Elements 920 are the detected peaks in the inputaudio signal 900.

FIG. 9B is a flowchart of a technique to determine a high frequencyportion of the hearing transfer function, according to one embodiment.In step 930, the processor 8, 44, and/or 88 identifies the transients inthe output sound, for example, by detecting the sound volume moving frombelow a threshold to a certain level above that threshold over thecourse of a few milliseconds. In step 940, the processor 8, 44, and/or88 determines the stimulated part of the cochlea by performing a Fourieranalysis to the first few milliseconds of the transient. For example, aFast Fourier Transform is performed on the first few milliseconds oftransients to identify the excited part of the cochlea (hypothetically 1kHz) in the loudness of the stimulus. In step 950, the processor 8, 44,and/or 88 checks whether the baseline noise from the sensor isacceptable; for example, whether it is less than 10 μV RMS, in the timeimmediately preceding the transient. In step 960, provided the noise onthe signal, such as an EEG signal, is acceptably low, the RMS value ofthe signal in time windows preceding and following the transient isrecorded. The frequency range and loudness of the transient and EEGamplitudes are saved to memory 46 and/or 90. In step 970, the processor8, 44, and/or 88 continuously repeats the above steps when the userlistens to music, to work out an average value for multiplefrequency/loudness pairs.

Multiple entries are collated for each frequency/loudness combination ora pool of nearby frequencies and loudnesses. The averaged pre-RMS andpost-RMS values are compared to response ranges from normal-hearing andhearing-impaired listeners to develop the high frequency hearingtransfer function for each ear.

As indicated above, comparisons of both amplitude and phase can becompared to response ranges from normal-hearing and hearing-impairedlisteners by the processor 8, 44, and/or 88 in order to develop thefrequency-dependent hearing transfer function for each ear of the user.OAEs and ASSRs can give a response phase in addition to signalmagnitude. In those embodiments where both amplitude and phase are used,one of these two techniques should be used. However, in otherembodiments of the invention where different AEPs may be evoked in theuser's ear, the processor 8, 44, and/or 88 may only be able to compareamplitude.

In those embodiments in which phase as well as amplitude is captured inthe hearing transfer function, the processor 8, 44, and/or 88effectively implements a finite input response (FIR) filter fitted withmagnitudes to minimize the effect of hearing loss and phase-shifts (forembodiments where phase information from the objective audiometricmeasures is available) to make the user's perception of the audio signalthe same as the perception of an ideal-hearing person.

In other embodiments, the frequency-dependent hearing transfer functionfor a user's ear is entirely composed of gains for each frequency bandas discussed previously, for example, 500, 1000, 2000 and 4000 Hz. Twopractical ways of setting the gains are firstly to simply set the gainaccording to the difference between detected audible threshold and theamplitude from the hearing transfer function of an ideal-hearingprofile. Secondly though, the relative amplitudes of the AEP/OAE atmultiple frequencies can be compared to one or more suprathreshold soundlevels. For example, if the amplitudes of the AEP/OAE at 500, 1000, 2000and 4000 Hz for an 80 dB stimulus are 120, 90, 100 and 110 units and anideal-hearing person's signal amplitudes should be 105, 100, 95 and 100units, then the equalizer gains are adjusted accordingly by theprocessor 8, 44, and/or 88. It will be appreciated that different usersmay have different head sizes, more hair, thicker skin, etc., so it isthe actual ratio between the values for the different frequencies ratherthan the absolute values that the processor 8, 44, and/or 88 compensatesfor, as depicted in FIGS. 6 and 7.

The measurement of both OAEs and AEPs can be timed in a number ofdifferent manners:

-   -   A complete hearing transfer function of the user's ears can be        made on request from the user.    -   A complete hearing transfer function of the user's ears can be        made the first time the user places the headphones on, or the        first time the user listens to audio.    -   A partial hearing transfer function can be measured each time        the user places the headphones on, or each time the user listens        to audio, which over time becomes a full hearing transfer        function; once a full hearing transfer function is complete,        further partial hearing transfer functions iteratively improve        the stored function.    -   Partial hearing transfer functions can be interleaved between        songs or during any time when audio is being input into the        device.

If implementing the cABR method of estimating an hearing transferfunction, the EEG recording is made continuously during any time audiois playing. Many hours of audio are required to acquire enough transientevents to estimate the high frequency part of the hearing transferfunction.

Any external or internal microphone can also be used to decide if theambient noise level is too high for accurate objective or psychophysicalmeasurements and measurements not made during such times.

Accuracy of the compensation applied during the equalization functioncarried out by the processor 8, 44, and/or 88 will be improved by thecollection of many examples of the hearing profiles of normal-hearingpersons and hearing-impaired persons. In that regard, the objective andpsychophysical audiometric data characterizing the audible threshold ofeach user of the headphones 10 or earbuds 70 can be transmitted to aremote database (not depicted). Upon collection of a sufficient numberof objective and psychophysical audiometric data of this type from asufficient number of users, greater accuracy in a normal-hearing personand a hearing-impaired person's frequency-dependent hearing transferfunction can be determined, and a normalized hearing transfer functioncan be input into the processor 8, 44, and/or 88, for example, bywireless or wired connection to the Internet by synching to a smartphoneapp, for subsequent storage in the memory 46 and/or 90. This normalizedhearing transfer function can then be used by the processor 8, 44,and/or 88 during the performance of the above-described functions.

Those skilled in the art will appreciate that there may be variationsand modifications of the configuration described herein that are withinthe scope of the present invention as defined by the claims appendedhereto.

For example, in other embodiments an hearing transfer function can alsobe derived by the processor 8, 44, and/or 88 from audiometric data usingmore complicated methods similar to those used in hearing aid fittingrules described in the following sources:

-   -   Pascoe, David Pedro. “Clinical measurements of the auditory        dynamic range and their relation to formulas for hearing aid        gain.” Hearing aid fitting: Theoretical and practical views        (1988): 129-152.        http://www.blog-audioprothesiste.fr/wp-content/uploads/2011/02/129-52-Pascoe-CLINICAL-MEASUREMENTS-OF-THE-AUDITORY-DYNAMIC-RANGE.pdf    -   Byrne, Denis, et al. “NAL-NL1 procedure for fitting nonlinear        hearing aids: Characteristics and comparisons with other        procedures.” JOURNAL-AMERICAN ACADEMY OF AUDIOLOGY 12.1 (2001):        37-51.        User Identification

FIG. 10 depicts an example of distortion-product OAE fine structure,according to one embodiment. The figure is adapted from Shaffer, LaurenA., et al. “Sources and mechanisms of DP-OAE generation: implicationsfor the prediction of auditory sensitivity.” Ear and hearing 24.5(2003): 367-379. Element 1000 is the cubic difference tone, and element1010 is the noise for inside a user's ear. Assume primary tone f1 islower in frequency and primary tone f2 is higher in frequency. When twopure tones f1 and f2 are presented to the human ear at the same time,the most prominent “distortion product” (DP) occurs at 2f1-f2—the “cubicdifference tone,” 1000. For example, if f1=1000 Hz and f2=1200 Hz, then2f1-f2=2(1000)−1200=2000−1200=800 Hz. Further, the cubic difference tone1000 is at least 50 dB less than f1, and the 2f1-f2 DP-OAE is largestwhen the ratio of f1 to f2 is about 1.22 and the intensities of f1=65 dBSPL and f2=50 dB SPL.

The cubic difference tone 1000 is generated from two separate siteswithin the cochlea, a primary and a secondary site, the signals fromeach constructively and destructively interfere with each other, makingcrests and troughs in the response. The pattern of the specificlocations (in the frequency domain) of the crests and troughs is calledfine structure and is unique to each ear. The cubic difference tone 1000response from a user can be compared to a plurality of cubic differencetones stored in a database. The database can be integrated into theheadphones 1, 10, 70, or it can be a remote database.

The processor 8, 44, and/or 88 compares the measured cubic differencetone 1000 and the plurality of cubic difference tones stored in thedatabase to identify the subject. The processor 8, 44, and/or 88 uses amatch score such as a root mean square error to make the comparison. Forexample, the processor, 8, 44, and/or 88 selects the cubic differencetone with the best match score, such as the cubic difference tone withthe lowest root mean square error. If the selected cubic difference tonematch score satisfies a specified threshold, such as the root meansquare error is below 25%, the match is found. If the selected cubicdifference tone does not satisfy the threshold requirement, noidentification/authentication is made. When a match is found, theprocessor retrieves a user ID associated with the matched cubicdifference tone.

According to one embodiment, biometric data associated with the user,such as the head with of the user, can be used to improve the accuracyof the identification. For example, if there are multiple cubicdifference tones that satisfy the specified threshold, the user can beidentified based on the quality of the match of the biometric data. Inanother example, if there are multiple cubic difference tones whose rootmean square error is within 5% of each other, the user can be identifiedbased on the quality of the match of the biometric data.

A user's perception of sound (i.e., the hearing transfer function) canbe measured using any of the above-disclosed methods, such as thesubjective method, AEP, EEG, etc. Each user hearing transfer function isunique. The user hearing transfer function is stored in the database,such as a database integrated into the headphones 1, 10, 70, or a remotedatabase. Similarly, the processor 8, 44, and/or 88 then compares themeasured hearing transfer function to the user hearing profiles in thedatabase to identify the subject.

Based on the subject identification, the headphones can modify the soundaccording to the user hearing profile, can load and play a playlistassociated with the identified user, etc. The user identification on itsown, or with other methods, can be used for security purposes as well.

Other types of objective data measured from the ear can also be used tofor identification such as the in-situ speaker frequency response ordata derived from the in-situ speaker frequency response, such as theacoustic impedance of the ear.

FIG. 11 depicts an embodiment of this invention where the OAE probe alsofunctions as a set of headphones for consumer audio use. The probe 1from FIG. 4B is duplicated on the other ear and connected to a wired orwireless analog or digital audio interface 1100. The microprocessor 1110controls measurement of the biometric profile and performs analysis. Ifno discrepancy is found, the audio information is routed to thespeakers.

Remarks

The foregoing description of various embodiments of the claimed subjectmatter has been provided for the purposes of illustration anddescription. It is not intended to be exhaustive or to limit the claimedsubject matter to the precise forms disclosed. Many modifications andvariations will be apparent to one skilled in the art. Embodiments werechosen and described in order to best describe the principles of theinvention and its practical applications, thereby enabling othersskilled in the relevant art to understand the claimed subject matter,the various embodiments, and the various modifications that are suitedto the particular uses contemplated.

While embodiments have been described in the context of fullyfunctioning computers and computer systems, those skilled in the artwill appreciate that the various embodiments are capable of beingdistributed as a program product in a variety of forms and that thedisclosure applies equally regardless of the particular type of machineor computer-readable media used to actually effect the distribution.

Although the above Detailed Description describes certain embodimentsand the best mode contemplated, no matter how detailed the above appearsin text, the embodiments can be practiced in many ways. Details of thesystems and methods may vary considerably in their implementationdetails, while still being encompassed by the specification. As notedabove, particular terminology used when describing certain features oraspects of various embodiments should not be taken to imply that theterminology is being redefined herein to be restricted to any specificcharacteristics, features, or aspects of the invention with which thatterminology is associated. In general, the terms used in the followingclaims should not be construed to limit the invention to the specificembodiments disclosed in the specification, unless those terms areexplicitly defined herein. Accordingly, the actual scope of theinvention encompasses not only the disclosed embodiments, but also allequivalent ways of practicing or implementing the embodiments under theclaims.

The language used in the specification has been principally selected forreadability and instructional purposes, and it may not have beenselected to delineate or circumscribe the inventive subject matter. Itis therefore intended that the scope of the invention be limited not bythis Detailed Description, but rather by any claims that issue on anapplication based hereon. Accordingly, the disclosure of variousembodiments is intended to be illustrative, but not limiting, of thescope of the embodiments, which is set forth in the following claims.

The invention claimed is:
 1. Headphones configured to personalize anaudio signal to a user, the headphones comprising: a speaker configuredto be proximate to a user's ear and to emit a content audio signal and atest audio signal, the test audio signal comprising a frequency in theaudible frequency range; an electrode configured to be proximate to theuser's ear and to measure an electrocochleography response associatedwith the user, the electrocochleography response comprising anelectrical signal generated in an inner ear or an auditory nerve of theuser in response to the test audio signal; a processor, coupled to thespeaker and to the electrode, the processor configured to: generate thetest audio signal; send the test audio signal to the speaker; receivefrom the electrode the electrocochleography response to the test audiosignal associated with the user; based on the test audio signal and theelectrocochleography response to the test audio signal, determine ahearing transfer function associated with the user; receive astatistical information representing data regarding human hearingprofiles; based on the hearing transfer function associated with theuser and the statistical information representing data regarding humanhearing profiles, adjust an amplitude associated with the content audiosignal to automatically compensate for a difference between a desiredhearing transfer function and the hearing transfer function associatedwith the user; and send the adjusted content audio signal to thespeaker.
 2. The headphones of claim 1, the hearing transfer functionassociated with the user derived from any of a hearing threshold of thefrequency in response to the test audio signal, an amplitude of theelectrocochleography response to the test audio signal, a phase-shift ofthe frequency in the electrocochleography response to the test audiosignal, and a latency of the electrocochleography response to the testaudio signal.
 3. The headphones of claim 1, the processor furtherconfigured to adjust any of a phase of the content audio signal, and alatency of the content audio signal to automatically compensate for thedifference between the desired hearing transfer function and the hearingtransfer function associated with the user.
 4. The headphones of claim1, the electrode forming a part of an earbud, eartip, earpad or headbanddisposed in a user's ear canal, face or head.
 5. A system comprising: aspeaker configured to be proximate to a user's ear and configured toemit an audio signal; a sensor configured to be proximate to the user'shead and configured to make an objective measurement of anelectrocochleography response associated with the user's hearingsensitivity to the audio signal, the electrocochleography responsecomprising an electrical signal generated in an inner ear or an auditorynerve of a user in response to the audio signal; a processor, coupled tothe speaker and to the sensor, the processor configured to: receive fromthe sensor the objective measurement associated with the user's hearingsensitivity to the audio signal; determine a hearing transfer functionassociated with the user based on the objective measurement of theelectrocochleography response and the audio signal; based on the hearingtransfer function associated with the user, adjust the audio signal toautomatically compensate for a difference between a desired hearingtransfer function and the hearing transfer function associated with theuser; and send the adjusted audio signal to the speaker.
 6. The systemof claim 5, wherein the audio signal comprises content audio signal. 7.The system of claim 5, the processor configured to adjust the audiosignal based on the hearing transfer function associated with the userand a statistical information representing data regarding human hearingprofiles.
 8. The system of claim 5, the sensor comprising an electrode,the electrode configured to: detect the electrocochleography responseassociated with the user, the electrocochleography response generated inresponse to the audio signal; and determine any of a hearing thresholdassociated with the electrocochleography response corresponding to afrequency associated with the audio signal, an amplitude of theelectrocochleography response corresponding to the frequency associatedwith the audio signal, a phase of the electrocochleography responsecorresponding to the frequency associated with the audio signal, and alatency of the electrocochleography response corresponding to thefrequency associated with the audio signal.
 9. The system of claim 5,the processor configured to transmit the hearing transfer functionassociated with the user from or to an external database.
 10. The systemof claim 5, the sensor comprising an electrode or a capacitive sensor.11. The system of claim 5, the sensor configured to: detect an auditoryevoked potential response associated with the user, the auditory evokedpotential response generated in response to the audio signal; anddetermine any of a hearing threshold associated with the auditory evokedpotential response corresponding to a frequency associated with theaudio signal, an amplitude of the auditory evoked potential responsecorresponding to the frequency associated with the audio signal, and alatency of the auditory evoked potential response corresponding to thefrequency associated with the audio signal.
 12. The system of claim 5,the processor further configured to continuously refine the hearingtransfer function associated with the user by refining the hearingtransfer function associated with a subset of frequencies in the hearingtransfer function.
 13. A method comprising: playing an audio signal to auser; making an objective measurement of an electrocochleographyresponse associated with the user's hearing sensitivity to the audiosignal, the electrocochleography response comprising an electricalsignal generated in an inner ear or an auditory nerve of the user inresponse to the audio signal; determining a hearing transfer functionassociated with the user based on the objective measurement of theelectrocochleography response and the audio signal; based on the hearingtransfer function associated with the user and a statistical informationrepresenting data regarding human hearing profiles, adjusting the audiosignal to automatically compensate for a difference between a desiredhearing transfer function and the hearing transfer function associatedwith the user; and sending the adjusted audio signal to a speaker. 14.The method of claim 13, wherein the hearing transfer function is derivedfrom any of an amplitude of a frequency in the objective measurementassociated with the user's hearing sensitivity to the audio signal, ahearing threshold of the frequency associated with the objectivemeasurement, a phase-shift of the frequency in the objective measurementassociated with the user's hearing sensitivity to the audio signal, anda latency of the electrocochleography response in the objectivemeasurement associated with the user's hearing sensitivity to the audiosignal.
 15. The method of claim 13, further comprising: performingin-situ calibration of the speaker to account for variations indifferent users' ears and variations in a placement of an earbud. 16.The method of claim 13, wherein said determining the hearing transferfunction comprises: combining a plurality of responses to the audiosignal.
 17. The method of claim 13, wherein making the objectivemeasurement comprises measuring the electrocochleography response whilethe user listens to the audio signal.
 18. The method of claim 13,wherein making the objective measurement comprises: detecting theelectrocochleography response associated with the user, theelectrocochleography response generated in response to the audio signal;and determining any of a hearing threshold associated with theelectrocochleography response corresponding to a frequency associatedwith the audio signal, an amplitude of the electrocochleography responsecorresponding to the frequency associated with the audio signal, a phasemeasurement of the electrocochleography response corresponding to thefrequency associated with the audio signal, and a latency of theelectrocochleography response corresponding to the frequency associatedwith the audio signal.